This study will attempt to determine if family members (parents, siblings, offspring, and spouses) of newly hospitalized cases of ulcerative colitis and proctitis, regional enteritis and Crohn's disease of the colon presently have or have previously had greater incidence of these diseases than family members of controls. Newly hospitalized cases will be ascertained through a concurrent inflammatory bowel disease (I.B.D.) case register in Baltimore and through the cooperation of local hospitals. Medical records of cases and family members will be abstracted, and the abstracts will be reviewed by a gastroenterologist. Cases and family members will be interviewed regarding histories of previous illnesses and hospitalizations; tobacco, alcohol, and dietary habits; and various demographic characteristics including marital history, educational background, and social activities. Information will be obtained concerning all family members, living and dead. This information will be obtained directly from living family members about themselves, and, to the best extent possible, about family members who have died. Hospital controls who are residents of the Baltimore area will be matched by sex, color, and age to each case. Hospital controls and their family members will be interviewed in the same manner as cases, and medical records will be abstracted for these controls and members of their families. Neighborhood controls living on the same block as cases will be matched to cases by sex, color and age. These controls and their family members will be interviewed in the same manner as cases and hospital controls, and medical records will be obtained for these controls and their family members. Death certificates and any existing medical records will be obtained for all case and control family members who have died. Samples of blood will be collected from cases, hospital controls, neighborhood controls, and their family members. Aliquots of serum will be separated and frozen at minus 70 degrees C for future studies.